Rather than focus on the porn or the sexual act, how about trying to stimulate his mind? For example, present him with a romantic evening with a "stranger" ... Get dressed up as though you were going on a blind date with someone who you heard was very interesting. Use fake names. Take your own transportation and meet up at a public location. Don't allow yourself to slip up and remember you already know this man. Just keep up the illusion. And DON'T have sex on that first date. Play is coy and allow him to be mentally teased. You may even want to purchase yourself a pay phone that he can use to contact this "other" woman from time to time. And if it helps, you can even play the part of the suspicious wife when he comes home late :-)
And don't let him have sex with you on those nights. "Make" him go to his porn to get his thrill for the evening.

Do this for a while and let the tension build up in a natural way.
Eventually the "other" you and your H can set up a secret night in a hotel.
He needs to make sure he tells the wife you that it is something like a biz trip or a night out of town with the guys.

This is a technique I heard about from a couples therapist for porn addictions and they said it can work wonders for the relationship!